function myInstanceof(cur,targetObj){
    var curProto=cur.__proto__,
        targetPrototype=targetObj.prototype;
    while(true){
        if(curProto===null){
            return false
        }
        if(curProto===targetPrototype){
            return true
        }
        curProto=curProto.__proto__;
    }
}

export default myInstanceof